Mid-infrared broadband metamaterial absorber based on van der Waals material

Van der Waals materials, such as α-phase molybdenum trioxide (α-MoO₃), have promising prospects in modern optics technologies, such as nano-imaging, negative refraction, and infrared detection. Particularly, the natural hyperbolic properties of α-MoO₃ make it an excellent candidate for perfect absorber. Here, we propose a design method for achieving broadband absorption based on van der Waals material (α-MoO₃) in the mid-infrared band. The segmented cubic Hermite interpolation is used to generate various geometric structures. Numerical results show that the average spectral absorptance of the optimized structure is up to 0.993 in the wavelength range of 10.4-12.7 μm. The high absorption performance can be explained as the slow-light effect. The impact of incident angle on absorption performance is also investigated. Finally, we calculate the spectral absorptance of the proposed absorber when the crystal axes of α-MoO₃ are rotated in the x-y plane. Our findings pave a novel path for designing broadband absorbers based on van der Waals materials, particularly in the mid-infrared band.